Block
A collection of transactions bundled together and permanently added to the blockchain. Each block contains a timestamp, transaction data, a reference (hash) to the previous block, and a nonce. This chaining of blocks through cryptographic hashes is what makes the blockchain tamper-resistant.
“Bitcoin blocks are created approximately every 10 minutes and can contain thousands of transactions, each block limited to roughly 1 MB in size (up to 4 MB with SegWit).”
Blockchain
A distributed, append-only digital ledger that records transactions across a network of computers in a way that makes it cryptographically secured and practically impossible to alter historical records. Each block contains transaction data and is linked to the previous block through a cryptographic hash, forming an immutable chain.
Mining
The process of using computational power to validate transactions and add new blocks to a Proof of Work blockchain. Miners compete to solve a cryptographic puzzle (finding a hash below a target difficulty), and the first to succeed earns the block reward plus transaction fees. Mining secures the network by making it prohibitively expensive to attack.
Block Reward
The cryptocurrency awarded to a miner or validator for successfully creating a new block on the blockchain. Block rewards consist of newly minted coins (block subsidy) plus the transaction fees from all transactions included in the block. In Bitcoin, the block subsidy halves approximately every four years.
Nonce
A 'number used once' that serves two key purposes in blockchain: (1) In Proof of Work mining, the nonce is the variable miners change to produce a block hash below the target difficulty. (2) In transactions, the nonce is a sequential counter for each wallet address that prevents replay attacks and ensures transaction ordering.
Hash
A fixed-length alphanumeric string produced by passing data through a cryptographic hash function (like SHA-256). Hashes are one-way functions — they can convert any input into a unique fingerprint, but the original data cannot be recovered from the hash. Hashing is fundamental to blockchain security, mining, address generation, and data integrity verification.